The 'Great Swapathon' launched by Change4Life

The government's Change4Life programme is set to offer families in England £250 million worth of vouchers to encourage them to eat well and be active.

The programme's "Great Swapathon" will give families advice about nutrition, food vouchers and discounts on activities.

Families can answer a questionnaire on the Great Swapathon website in order to be eligible for the £50 vouchers.

Four million £50 vouchers will also be available from Asda and the News of the World.

A million vouchers will be offered through local businesses who have signed up to participate in the scheme.

Companies such as Unilever, Mars Weight Watchers and Mars have also pledged their support to the scheme.

Health secretary Andrew Lansley said: "It's a great example of how government, the media, industry and retailers can work together to help families to be healthy."

"The healthy option isn't always the cheapest option so it's a really important step to be able to offer £50 off healthier foods, drinks and activities."

However, experts have said they are concerned about large companies playing such an influential role in informing the public about what foods to eat.

Tim Lang, professor of food policy at City University, said: "I'm nervous if big companies are put in charge of public health - that's not to say they can't be good for public health - but if they are centrally involved in delivering it.